This invention relates generally to a sliding bearing having a back metal made of austenitic stainless steel, and more particularly to a sliding bearing which has a high strength and a high thermal expansion coefficient, and provides an effective countermeasure against the reduction of interference portions of the bearing which reduction results from a thin wall structure of the bearing and a light-alloy design of a bearing housing.
The interference portions are parts of the bearing, and are necessary for press-fixing the bearing to a casing. More specifically, in the case of a half sliding bearing A, the bearing A, before assembled together, project slightly from halves of the casing B, respectively, as shown by "C" in FIG. 2A. The thus projected portions C are referred to as the interference portions. When the bearing A is in its assembled condition, the bearing A is subjected to compression corresponding to the amount of the interference portions C, as shown in FIG. 2B, and in this condition the bearing A is press-fixed to the casing B, and assumes a true cylindrical shape. For measuring the amount of the interference portions C, there is prepared a model having a diameter identical to the inner diameter of the casing B, and each half of the bearing A is press-fitted in the inner surface of the model under a predetermined pressure. The length of projecting of the half sliding bearing from the model is measured, and the value of measured projected length is defined to be the amount of the interference portion.
A conventional sliding bearing comprises a back metal of low-carbon steel, and a bearing alloy bonded to back metal. A bearing housing is also made of low-carbon steel. Therefore, the back metal and the housing are analogous in thermal expansion coefficient to each other, and even when the temperature rises during the operation of the bearing, the bearing and the housing are held in intimate contact with each other, with no gap developing therebetween. Thus, there has been no particular problem.
With respect to a big end bearing and a main bearing for an internal combustion engine, in order that a half sliding bearing can be held in intimate contact with a bearing housing, the bearing is assembled with a large interference. Particularly, recently, the bearing housing has increasingly been made of a light alloy to meet a lightweight design cf the engine. In this case, in a high-temperature condition, the housing of an aluminum alloy (thermal expansion coefficient: 20.times.10.sup.-6 /.degree. C.) expands to a greater extent than the back metal of low-carbon steel (thermal rexpansion coefficient; 13.5.times.10.sup.-6 /.degree. C.), so that the interference of the bearing is reduced. Therefore, the bearing can not follow the deformation of the housing caused by a temperature rise during a high-speed operation, and as a result a gap develops between the two. In order to avoid this difficulty, a greater interference is required; however, the resiliency of the low-carbon steel back metal and the rigidity of the housing are limited, and this results in a problem that the lightweight design can not be achieved easily.